1. Field of the Invention
The present invention relates to an electronic transaction system using an electronic check, and an issue system and an examination system for the electronic check.
2. Description of the Related Art
FIG. 1 is a flowchart of an electronic transaction for online shopping or the like among a consumer, a bank/credit card company and a merchandiser.
A consumer completes an electronic purchase application and specifies how to settle the account (S11). When the consumer choses to pay by bank transfer or a credit card, he writes his bank account number or his credit card number in the application.
When the application is transferred to a merchandiser (S12), the merchandiser confirms the contents of the application and makes inquiries at a paying agent, that is, the bank or the credit card company, about whether the account can be settled by the method specified by the consumer (S13).
If the consumer""s balance at the bank account or the consumer""s overdraft at the bank or the credit card company exceeds the payment so that the consumer is solvent, the bank or the credit card company settles the account (S14). Before or after the payment, the goods are sent to the consumer, and the transaction is concluded (S15). However, if the consumer is insolvent, the transaction falls through (S16).
In the conventional electronic commerce as above, private information such as a bank account number and a credit card number are informed to a merchandiser in every transaction. Therefore, the risks of leakage of the private information and illegal use of the private information are always involved. In addition, it is difficult to detect an illegal transaction through such illegal use of private information.
Owing to such risks, the reliability on the electronic commerce is low. Furthermore, the upper limit of an amount of money dealt with in the electronic commerce is suppressed so as to minimize a damage caused by the illegal use of private information.
On the other hand, electronic commerce conducted through a leased line has a high reliability, but is not widely utilized because only a limited number users can access the leased line.
An, an electronic transaction system of for circulating digital cash has been proposed (U.S. Pat. No. 4,759,063, etc.). The ""063 patent discloses the fundamental principle of digital cash utilizing a blind signature is based on the RSA cryptosystem. First, a user generates an arbitrary numeral X corresponding to his own signature, and a random numeral R, and calculates these numerals with a public key of a bank. The result of the calculation, that is, an enciphered data, is sent to the bank. The bank cannot obtain the arbitrary numeral X corresponding to the signature of the user because the enciphered data has been obtained on the basis of the calculation using the random numeral. Under this condition, the bank adds to the data a digital signature corresponding to an amount of money by using its own private key, and the resultant data is sent back to the user. The user obtains the numeral X added with the digital signature of the bank from the enciphered data with the bank signature by using his own public key, namely, obtains the money, which is to be used for the payment.
In order to circulate the digital cash using a blind signature, it is necessary to unify the format of data to be transferred in the electronic transaction system because a signature as well as an amount of money should be enciphered. In addition, since a complicated method is required for the encryption, the electronic transaction system becomes large scale. Therefore, a general user cannot easily introduce such a large scale system. Furthermore, since the amount of money is unitized in a predetermined unit, an arbitrary amount of money cannot be dealt with.
Furthermore, a lot of banks in the North America have established the FSTC (Financial Services Technology Consortium) and are trying to provide electronic check services on INTERNET (pp. 78-85, xe2x80x9cNikkei Communicationsxe2x80x9d, 1996.1.1). The mechanism of the electronic check is that when a consumer, who holds a serially numbered checkbook, inputs data in an order sheet on a screen offered by a merchandiser, the consumer also inputs an amount and the serial number of the checkbook on a check on the screen and adds an electronic signature by his own private key based on the RSA cryptosystem. The merchandiser confirms that the consumer is genuine by checking an open key of the consumer, then transmits the electronic check to a bank to cash the check.
However, it is unknown whether the consumer is solvent for the amount of the check in the above system when the consumer inputs the amount. Consequently, the payment is not guaranteed until the check is to be cashed, whereby the upper limit of the amount in the transaction is suppressed in order to prevent the risk.
The present invention was devised to overcome the aforementioned problems.
In the electronic transaction system of this invention, an electronic check including an electronic signature of an issuer and information on an account to be settled is issued by the issuer apparatus to a drawer apparatus in response to a demand from the drawer apparatus; the drawer adds his electronic signature to the issued electronic check, so as to make the electronic check settleable; a payee apparatus of the electronic check which has been made settleable by the electronic signature of the drawer examines the electronic signature of the drawer included in the electronic check, so as to certify the drawer of the electronic check; and a paying agent apparatus examines the contents of the electronic check which is demanded to be settled by the payee apparatus of the electronic check, so as to determine whether the electronic check is settleable, and settles the account when it is settleable.
Alternatively, in the electronic transaction system of this invention, an electronic check including an electronic signature of an issuer and information on a sum to be settled is issued by the issuer apparatus to a drawer apparatus in response to a demand from a payee apparatus; the drawer adds his electronic signature to the issued electronic check so as to make the electronic check settleable; and a paying agent apparatus examines the contents of the electronic check which has been made settleable by the electronic signature of the drawer, so as to determine whether the electronic check is settleable, and settles the account when it is settleable.
Furthermore, in the electronic transaction system of the invention, an electronic check with an electronic signature is circulated among the parties concerned. Private information such as a bank account number, a credit card number and a credit level is prevented from leaking. The electronic check on which the electronic signature is added by using a public key cryptosystem is practically impossible to be altered and forged, and in addition, the electronic check is unsettleable until a drawer adds his own electronic signature. Therefore, cashing on an illegal demand can be prevented.
Furthermore, in the electronic transaction system of the invention, the electronic check can be transmitted and received through a widely used communication system such as an electronic mail system. Therefore, the system can be configured at a low cost and can be utilized by a general user without leasing a line.
Additionally, in the electronic transaction system of the invention, the settlement can be guaranteed because the drawer confirms the sum to pay before adding his electronic signature.
Further, in the electronic transaction system of the invention, the payment is surely guaranteed because an issuer issues an electronic check adding his electronic signature after certifying solvency of a drawer for an amount on the electronic check, which is previously indicated by the drawer.
Moreover, in the electronic transaction system of the invention, there is no need for a drawer to demand for the issue of an electronic check.
Furthermore, in the electronic transaction system of the invention, settlement for one electronic check twice is prevented.
Further, in the electronic transaction system of the invention, illegal conversion by a demander who is not an inherent payee can be avoided.
The electronic check of this invention includes an electronic signature by the public key cryptosystem, and hence it is practically impossible to alter and forge the electronic check. In addition, the electronic check cannot be settled until a drawer adds his own electronic signature. Therefore, illegal conversion on a dishonest demand can be prevented.
Additionally, in the system of this invention for issuing an electronic check, there is no need for a drawer to demand the issue of an electronic check.
Furthermore, in the system of this invention for issuing an electronic check, double issue of an electronic check can be avoided.
In addition, an electronic check issued by the system of this invention for issuing an electronic check is prevented from being illegally converted by a demander who is not an inherent payee.
In the system of this invention for examining an electronic check, the legality of a drawer of an electronic check can be determined on the basis of the calculation on an electronic signature contained in the electronic check with a computer, so as to confirm the legality of the drawer of the electronic check, that is, a payer, in a short period of time. Additionally, the system can be easily automated.
Furthermore, in the system of this invention for examining an electronic check, double settlement of one electronic check can be prevented.
Additionally, in the system of this invention for examining an electronic check, dishonest conversion by a demandant who is not an inherent payee can be avoided.
Accordingly, an object of the invention is to provide an electronic transaction system and a system for issuing an electronic check, in which an electronic check circulated among the parties concerned is practically impossible to alter and forge, so as to prevent illegal conversion; in which private information such as a bank account number and a credit card number is prevented from leaking to a third party; which can provide its service through a widely used communication system; and in which the settlement can be guaranteed.
Additionally, another object of the invention is to provide a system for examining an electronic check which can determine the legality of an electronic check on the basis of calculation with a computer, can be easily automated and can prevent illegal conversion by a dishonest demander.
The above and further objects and features of the invention will more fully be apparent from the following detailed description with accompanying drawings.